Abstract:

The Deepwater Horizon (DWH) oil spill was the largest in U.S. history – the toxicity of DWH polycyclic aromatic hydrocarbons (PAHs) is well-established, but a knowledge gap exists regarding how they affect the vertebrate stress axis. We hypothesized that 1) marine vertebrates exposed to DWH PAHs experience stress axis impairment, and that co-exposure to an additional stressor may exacerbate these effects, 2) 5-HT may act as a secondary cortisol secretagogue in DWH PAH-exposed fish to compensate for impairment, and 3) the mechanism of stress axis impairment would be either a decrease in MC2R functionality or total kidney cholesterol concentration. In vivo plasma cortisol, plasma ACTH, plasma 5-HT concentrations in Gulf toadfish exposed to environmentally relevant DWH PAH concentrations for 7 days with or without exposure to chronic simulated predator stress was measured. In vitro cumulative kidney cortisol secretion in response to ACTH or 5-HT in kidneys from control or PAH exposed fish were tested. Furthermore, kidney cAMP and cholesterol concentrations and kidney mRNA expression of CYP1A and steroidogenic proteins (StAR, 11-beta-hydroxylase, P450scc) in control and PAH-exposed fish were analyzed. Experiments were completed at RSMAS, University of Miami, MTLSS building rm. 211. Experiments were started in November 2019 and completed in March 2020.

Suggested Citation:

Milton, Emily and Maria Cartolano. 2021. Acute exposure: a more in-depth analysis of DWH oil impacts on vertebrate stress axis endpoints. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-4ra1-g957

Purpose:

The purpose of this work was to determine the mechanisms of stress axis impairment on vertebrates.

Data Parameters and Units:

Replicate fish ID, Mass, Sex (M/F), GSI, Plasma cortisol (ng/ml), Plasma ACTH (pg/ml), Plasma serotonin (ng/ml), bath cortisol concentrations (ng/ml), cAMP concentration (pmol cAMP/mg total protein), cholesterol concentration (mg/g kidney), kidney CYP1A mRNA expression, kidney StAR mRNA expression, kidney 11 Beta hydroxylase mRNA expression, Kidney P450scc mRNA expression. LEGEND Replicate Fish ID AXXX-B-C-DZ A Treatment (C = control; H = high concentration exposure) XXX Fish number (257-310) B Trial # (3 or 4) C Fish state (Not stressed [NS] or Chronically stressed [CS]) D Time sample taken in days (d) or months (m) Z Period sample taken (either during Exposure [E] or during Recovery [R]) nd not determined The headers are: Replicate fish ID, Mass, Sex (M/F), GSI, Plasma cortisol (ng/ml), Plasma ACTH (pg/ml), Plasma serotonin (ng/ml), bath cortisol concentrations (ng/ml), cAMP concentration (pmol cAMP/mg total protein), cholesterol concentration (mg/g kidney), kidney CYP1A mRNA expression, kidney StAR mRNA expression, kidney 11 Beta hydroxylase mRNA expression, Kidney P450scc mRNA expression.

Methods:

Fish were exposed to flow-through control or environmentally realistic PAH concentrations (~3 ug/L sum total 50 PAHs) for 7 days. A subset of fish was chased daily so that they were chronically stressed. After exposure, blood and kidney samples were taken and analyzed.

Individual Files: